February 11, 2009

Taking a Cell's Temperature

Looking beyond the genetics and proteomics of individual cells to examine properties that might seem less important can actually lead to some interesting results.

For example, researchers who poked cells with the tip of an atomic-force microscope (AFM) found that aggressive cancer cells are softer than their healthy counterparts–a property that may help them journey through the circulatory system to spread the disease. In this way, AFM technology, traditionally one of the tools of mechanical engineers and materials scientists, may help doctors determine how aggressive a patient’s cancer is. As TR reported last week, the same microscopy technique is also being used to study osteoarthritis in its early stages.

Now researchers at the University of Tokyo have developed an imaging probe that takes individual cells’ temperature to within half a degree centigrade. As the temperature rises, the probe–a green fluorescent dye encased in a nanogel–shines more brightly. The Japanese researchers haven’t worked out how measuring a cell’s temperature might help clinicians deal with disease. But the findings were somewhat surprising, according to an outside researcher contacted by Chemistry World. The article quotes Prasanna de Silva from the University of Queens, who was not involved in the research:

“I think people might have felt before that temperature was not worth
measuring,” [says] de Silva, “because we expect it to be held constant
most of the time. We are beginning to realise that, while the cell’s
buffering mechanisms do eventually work, there are short-term local
effects. So if you can watch a cell in small spatial detail, with good
time resolution then you can pick up on things which wouldn’t be seen
otherwise.”

The temperature-sensitive probe is described this week in Journal of the American Chemical Society. The researchers speculate that diseased cells may run slightly hotter because of increased metabolism, and they hope to formulate the temperature probe so that cells can be monitored as they grow.

Last year, I wrote about another research group using voltage-sensitive dye nanoparticles to study the electrical fields inside cells, which can be as strong as lightning bolts. It’s not yet clear just what the implications of either imaging technique will be. But for the voltage-sensing story, I talked to Piotr Grodzinski, director of the National Cancer Institute Alliance for Nanotechnology in Cancer, who emphasized the importance of studying cancer at the cellular level. Here’s a snippet from that article:

Grodzinski says that many developments in cancer research over the past few years have been “more reactive,” working toward developing diagnostics for catching the disease in its earlier stages and for better predicting to which drugs patients will respond. Despite how far cancer treatments have come, the way that cancer progresses at the cellular level is still not very well understood. With a better understanding, researchers hope to further improve diagnostics and personalized care. “This development represents an attempt to start using nanoscale tools to understand how disease develops,” says Grodzinski.